/Engine/Plugins/Experimental/Mutable/Source/CustomizableObject/Public/MuCO/CustomizableObjectInstanceDescriptor.h
Increases the range of values of the projector with ParamName, returns the index of the new projector value, -1 otherwise. The added value is initialized with the default projector as set up in the editor and is the last one of the range.
int32 AddValueToProjectorRange ( const [FString](API\Runtime\Core\Containers\FString) & ParamName )